Electric resistance



March 13, 1934. E. GINDRE 1,950,606

4 ELECTRIC RESISTANCE Filed Oct. 25, 1931 EUGENE GINDRE- INVENTOR ATTORNEYS Patented 13, 1934 f 1,950,606

UNITED STATES PATENT OFFIICE 1,950,606 ELECTRIC imsIs'rANoE Eugene Gindre, Gennevilliers, France, assignor to Socit Anonyme De Cal-bone, Gennevilliers, France Application October 23, 1931, Serial No. 570,565

, In France March 26, 1931 v 4 Claims. (Cl. 201-51) As is well known, electric resistances have been stead of being bounded by two plane surfaces, made by means of a pile of carbon discs or washhas two conical surfaces b and c, the angle at ers, and the resistance has been varied by modithe apex of I) being greater than that at the apex fying the mechanical pressure exerted, on this of c.

5 pile. To a small pressure corresponds a high It results therefrom, that, when two blocks are resistance and, when the pressure increases, the fitted into each other, Fig. 3, they are in contact resistance diminishes. only at their periphery. A pile of blocks pre- It will easily be understood why by increassents a high electric resistance, but when an ending the pressure, the resistance is diminished. wise pressure is exerted on this pile, each of these 10 The discs or washers placed one on the other are blocks is distorted owing to its resiliency and the only in contact at a small number of points. The zones of contact increase until the surfaces 12 and electric resistance is therefore very high when a are entirely in contact.

there is no pressure. But, if a pressure is ex- Instead of conical surfaces, the faces of the erted, the discs or washers are distorted owing blocks can be of different shape. They can con- 15 to their resiliency; the surface area in contact stitute for instance pyramids, or generally speak- Z0 is considerably increased and the resistance pr0-= ing, any surface such that, without pressure, there portionally diminishes. is contact only at the periphery and there is be- In the various applications of resistances of tween adjacent blocks a space increasing in this type, it is usually desired that the increase height towards the centres of the blocks.

go of resistance should be very rapid. For obtain- The contour of the block can be of any shape,

ing this, it has been suggested to make very thin round, square, oval or the like. and consequently very resilient washers which are The new device presents important advantages. very easily distortable, but these washers are Firstly, the blocks are easily assembled owing very fragile and break very easily. to their shape. The entire structure has natu- 35 Now, the heat due to the passage of the cur= rally a great stability. The blocks need not even rent is dissipated only by the side surface oi 'the' be guided. However, it is desirable to hold the discs or washers. It results that a thin disc or column either by means of side guides, or by washer is costly relatively to the amount of heat placing it in a tube, or by threading the'blocks, it is capable of dissipating. This is another inperforated at their centre, on a spindle, etc.

30 convenience of thin discs or washers in addition Another characteristic advantage of the inven- 86 to their fragility. tion consists in the rapid diminution of the elec- The present invention has for its object to protric resistance'with the pressure, and reversely. vide a device in which the electric resistance may 1 Moreover, the variation of resistance is continbe rapidly varied without having to use thin uous; the new resistances avoid the well known '5 discs or washers. disadvantages of rheostats provided with contact 90 According to the invention each resistance elepieces, in which the interval between two contact ment consists of a block having surfaces of two pieces is relatively large. different contours, so that when two blocks are Moreover in such rheostats the contact pieces fitted together and no pressure is exerted, the are subject to rapid wear whereas the new device 3 two adjacent blocks are in contact only at their does not require any maintenance, as it is not periphery and there is between themra space insubjected to any wear. creasing towards the centre of the block. Owing The resistance blocks constituted as Just stated to this arrangement, the blocks, although thick, are very strong and do not break under the accan be resiliently distorted, without breaking, and tion of the pressures to which they are subjected. produce a rapid variation of the ohmic resist- The new resistances are capable of receiving ance. numerous applications, for instance for the small In. order that the invention may be clearly unmotors of sewing machines, for the dynamos used derstood, the accompanying drawing illustrates for lighting railway trains, for adjusting the volta form of construction, in the particular case in age of generators, for the dynamos of motor cars.

50 which the blocks have conical surfaces. They are as useful for large as for small machines Fig. 1 is an elevation of a resistance block. and can be used as energizing rheostats, etc. Fig. 2 is a corresponding plan view. The above arrangements are given by way of Fig. 3 shows a pile of blocks fitted in each exampleonly; the details of construction, forms, other. dimensions and materials used may be varied 55 As illustrated in the drawing, each block a, :inaccording to circumstance without departing thereby from the scope of the invention.

I claim: r

1. Acarbon pile resistance adapted to be subiected to pressure, comprising a series of super posed carbon disks wherein each disk has a 0on cavesurface upon one side and a convex surface upon the other side, and arranged so that the concave surface of each disk directly faces the adJacent convex surface of the next disk in the series and the disks make mutual contact solely at the peripheries thereof.

2. A carbon pile resistance adapted to be subjected to pressure, comprising a nested series of superposed carbon disks wherein each disk has a conical concave surface upon one side and a conical convex surface upon, the other side, and arranged so that the conical concave surface of each disk directly faces'the'adjacent conical convex jected to pressure, comprising a nested series of superposed carbon disks wherein each disk has a conical concave surface of a predetermined inclination upon one side and a conical convex surface of a different inclination upon the other side,

and arranged sothat the conical concave surface smaller apex angle upon one side and a conical convex surface forming a relatively greater apex anglejupon the other side, and'arranged so that the conical concave surface of each disk directly faces the adjacent conical convex surface of the next disk in the series and the disks make mutual contact solely at the peripheries thereof. EUGENE GINDRE.

a conical concave surface forming a relatively 

